Templating induced behavior of platinum-free carbons for oxygen reduction reaction

• Pt-free C-based catalysts for ORR were prepared using various templating methods.
• Electrochemical and BET analyses were performed.
• ORR features depend on pore size and pore shape.
• A combination of meso and micropores is useful to ORR behavior.
• Ink-bottle pores are detrimental to ORR.

The aim of this work is to investigate the effect that pore shape and morphology may introduce in the behavior of some platinum free catalysts for the oxygen reduction reaction (ORR). Samples of the catalyst are obtained heat-treating a reactant mixture with constant composition and using a variety of templating procedures, i.e. shape-imprinting materials (like high surface area silica and Black Pearls 2000), and some self-templating processes (freeze-drying and in-situ generation of gas bubbles). Reaction products are characterized by XPS, BET and electrochemical methods. Analysis of results shows that the ORR catalyst activity depends in a complex manner on structural and morphological features, being not only affected, as expected, by surface area and pore width, but also by the pore shape. In a detailed examination a relation in fact emerges between ORR activity and relative abundance of micro- and mesopores of different size and pore shape.

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